I haven't had reliability issues with BitBucket. My main complaint is it's just really difficult to use.

I just find my time in GitHub is smoother and easier. For example comparing branches/tags to each other... in GitHub if you open a release from a week ago, there will be a link "this is 12 commits behind your main branch" and you can just click it to view the code in those commits.

BitBucket doesn't even have releases. They just have tags which can trigger pipelines. Functionality wise, it's the same thing. But from an ease of use perspective GitHub is so much faster and easier to navigate as long as your project follows standard branching/tagging/etc practices (which it should, especially if you're working on a team).